Powdered Titanium Alloy Composition and Article Formed Therefrom

ABSTRACT

A titanium alloy composition that includes, other than impurities, about 7.0 to about 9.0 percent by weight vanadium (V), about 3.0 to about 4.5 percent by weight aluminum (Al), about 0.8 to about 1.5 percent by weight iron (Fe), about 0.14 to about 0.22 percent by weight oxygen (O), optionally about 0.8 to about 2.4 percent by weight chromium (Cr), and the balance titanium.

FIELD

This application generally relates to titanium alloys and, moreparticularly, to titanium alloys for powder metallurgy.

BACKGROUND

Titanium alloys offer high tensile strength over a broad temperaturerange, yet are relatively light weight. Ti-6Al-4V is perhaps the mostcommon and widely used titanium alloy. In wrought form, Ti-6Al-4V has arelatively low density (about 4.47 g/cm³), yet exhibits exceptionalmechanical properties, such as a yield strength in excess of 120 ksi(thousand pounds per square inch), an ultimate tensile strength inexcess of 130 ksi, an elongation of at least 10 percent, and a fatiguelimit (10 million plus cycles) in excess of 90 ksi. Furthermore,titanium alloys are resistant to corrosion. Therefore, titanium alloys,Ti-6Al-4V specifically, are used in various demanding applications, suchas aircraft components, medical devices and the like.

Powder metallurgy manufacturing techniques, such as die pressing, metalinjection molding, direct hot isostatic pressing and the like, result inthe formation of net (or near net) articles. Therefore, powdermetallurgy manufacturing techniques offer the opportunity forsignificant cost savings by significantly reducing (if not completelyeliminating) the need for machining operations, which are time intensiveand wasteful of materials.

Ti-6Al-4V powders are available, and have been formed into variousarticles using powder metallurgy manufacturing techniques. However,articles formed from Ti-6Al-4V powders do not have the same mechanicalproperties as articles formed from wrought Ti-6Al-4V. For example, thefatigue limit of articles formed from Ti-6Al-4V powders can be 20 to 30percent less that the fatigue limit of articles formed from wroughtTi-6Al-4V (e.g., 70 ksi for powdered versus 95 ksi for wrought). In manyapplications, such a significant reduction in the fatigue limit may notbe acceptable.

Accordingly, those skilled in the art continue with research anddevelopment efforts in the field of titanium alloys.

SUMMARY

In one embodiment, the disclosed titanium alloy consists essentially ofabout 7.0 to about 9.0 percent by weight vanadium (V), about 3.0 toabout 4.5 percent by weight aluminum (Al), about 0.8 to about 1.5percent by weight iron (Fe), about 0.14 to about 0.22 percent by weightoxygen (O), optionally about 0.8 to about 2.4 percent by weight chromium(Cr), and the balance titanium.

In another embodiment, the disclosed titanium alloy consists essentiallyof about 7.0 to about 8.5 percent by weight vanadium (V), about 3.5 toabout 4.5 percent by weight aluminum (Al), about 0.9 to about 1.5percent by weight iron (Fe), about 0.15 to about 0.22 percent by weightoxygen (O), and the balance titanium.

In another embodiment, the disclosed titanium alloy consists essentiallyof about 7.5 to about 9.0 percent by weight vanadium (V), about 3.0 toabout 4.0 percent by weight aluminum (Al), about 0.8 to about 1.3percent by weight iron (Fe), about 0.14 to about 0.20 percent by weightoxygen (O), about 0.8 to about 2.4 percent by weight chromium (Cr), andthe balance titanium.

In one embodiment, the disclosed powdered titanium alloy compositionconsists essentially of about 7.0 to about 9.0 percent by weightvanadium (V), about 3.0 to about 4.5 percent by weight aluminum (Al),about 0.8 to about 1.5 percent by weight iron (Fe), about 0.14 to about0.22 percent by weight oxygen (O), optionally about 0.8 to about 2.4percent by weight chromium (Cr), and the balance titanium.

In another embodiment, the disclosed powdered titanium alloy compositionconsists essentially of about 7.0 to about 8.5 percent by weightvanadium (V), about 3.5 to about 4.5 percent by weight aluminum (Al),about 0.9 to about 1.5 percent by weight iron (Fe), about 0.15 to about0.22 percent by weight oxygen (O), and the balance titanium.

In another embodiment, the disclosed powdered titanium alloy compositionconsists essentially of about 7.5 to about 9.0 percent by weightvanadium (V), about 3.0 to about 4.0 percent by weight aluminum (Al),about 0.8 to about 1.3 percent by weight iron (Fe), about 0.14 to about0.20 percent by weight oxygen (O), about 0.8 to about 2.4 percent byweight chromium (Cr), and the balance titanium.

Other embodiments of the disclosed titanium alloy composition willbecome apparent from the following detailed description, theaccompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram depicting one embodiment of the disclosedmethod for manufacturing an article;

FIG. 2 is a flow diagram of an aircraft manufacturing and servicemethodology; and

FIG. 3 is a block diagram of an aircraft.

DETAILED DESCRIPTION

Disclosed is an alpha-beta titanium alloy that may be used in wrought orpowdered form. Significantly, articles formed from the disclosedtitanium alloy using powder metallurgy manufacturing techniques may havemechanical properties, such as fatigue limit, that are at least as goodas (if not better than) the mechanical properties of articles formedfrom wrought Ti-6Al-4V. Therefore, the disclosed titanium alloy is analternative to Ti-6Al-4V that is particularly suitable for use in powdermetallurgy.

In a first embodiment, disclosed is an alpha-beta titanium alloy havingthe composition shown in Table 1.

TABLE 1 Element Range (wt %) Vanadium 7.0-9.0 Aluminum 3.0-4.5 Iron0.8-1.5 Oxygen 0.14-0.22 Chromium 0 or 0.8-2.4 Titanium Balance

Chromium (Cr) is an optional component of the alpha-beta titanium alloyof the first embodiment. When present, the concentration of chromium mayrange from about 0.8 percent by weight to about 2.4 percent by weight,such as from about 1.8 percent by weight to about 2.4 percent by weight.

Thus, the alpha-beta titanium alloy of the first embodiment consistsessentially of titanium (Ti), vanadium (V), aluminum (Al), iron (Fe),oxygen (O) and, optionally, chromium (Cr).

Those skilled in the art will appreciate that various impurities, whichdo not substantially affect the physical properties of the alpha-betatitanium alloy of the first embodiment, may also be present, and thepresence of such impurities will not result in a departure from thescope of the present disclosure. For example, the impurities content ofthe alpha-beta titanium alloy of the first embodiment may be controlledas shown in Table 2.

TABLE 2 Impurity Maximum (wt %) Carbon 0.10 Nitrogen 0.05 Chlorine 0.05Hydrogen 0.015 Silicon 0.05 Yttrium 0.005 Sodium 0.01 Magnesium 0.10Other Elements, Each 0.10 Other Elements, Total 0.30

In a second embodiment, disclosed is an alpha-beta titanium alloy havingthe composition shown in Table 3.

TABLE 3 Element Range (wt %) Vanadium 7.0-8.5 Aluminum 3.5-4.5 Iron0.9-1.5 Oxygen 0.15-0.22 Titanium Balance

Thus, the alpha-beta titanium alloy of the second embodiment consistsessentially of titanium (Ti), vanadium (V), aluminum (Al), iron (Fe) andoxygen (O). The impurities content of the alpha-beta titanium alloy ofthe second embodiment may be controlled as shown in Table 2.

One specific, non-limiting example of a titanium alloy of the secondembodiment has the composition shown in Table 4.

TABLE 4 Element Target (wt %) Vanadium 7.5 Aluminum 4.0 Iron 1.2 Oxygen0.20 Titanium Balance

In a third embodiment, disclosed is an alpha-beta titanium alloy havingthe composition shown in Table 5.

TABLE 5 Element Range (wt %) Vanadium 7.5-9.0 Aluminum 3.0-4.0 Chromium0.8-2.4 Iron 0.8-1.3 Oxygen 0.14-0.20 Titanium Balance

Thus, the alpha-beta titanium alloy of the third embodiment consistsessentially of titanium (Ti), vanadium (V), aluminum (Al), chromium(Cr), iron (Fe) and oxygen (O). The impurities content of the alpha-betatitanium alloy of the third embodiment may be controlled as shown inTable 2.

One specific, non-limiting example of a titanium alloy of the thirdembodiment has the composition shown in Table 6.

TABLE 6 Element Target (wt %) Vanadium 8.0 Aluminum 3.5 Chromium 2.0Iron 1.0 Oxygen 0.18 Titanium Balance

In one variation of the third embodiment, the disclosed alpha-betatitanium alloy may have the composition shown in Table 7.

TABLE 7 Element Range (wt %) Vanadium 7.5-9.0 Aluminum 3.0-4.0 Chromium1.8-2.4 Iron 0.8-1.3 Oxygen 0.14-0.20 Titanium Balance

The disclosed titanium alloy may be used to manufacture variousarticles, such as aircraft parts and components, using traditionalcasting or forging processes, or hybrid processes such as powdermetallurgy combined with forging, or rolling, or extrusion, or welding(solid state (linear or rotational friction or inertia) or traditionalmelting fusion or with filler). Additionally the disclosed titaniumalloys may be used for various net shape and near net shape fabricationprocesses such as additive manufacturing laser, electron beam, plasmaarc melting techniques and powder metallurgy additive laser or electronbeam sintering techniques. The disclosed titanium alloy may also be usedin powdered form to manufacture various articles using powder metallurgymanufacturing techniques. As noted herein, the powdered form of thedisclosed titanium alloy (the disclosed powdered titanium alloycomposition) is significantly attractive, particularly vis-a-visTi-6Al-4V in powdered form, due to an anticipated improvement in themechanical properties, particularly fatigue limit, of the resultingarticles.

Various powdered forms of the disclosed titanium alloy may be usedwithout departing from the scope of the present disclosure. Regardingshape, the powder particles of the disclosed powdered titanium alloycomposition may be spherical, flakey, spongy, cylindrical, blocky,acicular or the like. Powder particle shape may be substantially uniformthroughout the powdered titanium alloy composition (e.g., all sphericalparticles) or multiple different shapes may be included in a particularpowdered titanium alloy composition. Regarding size, the powderparticles of the disclosed powdered titanium alloy composition may havea broad particle size distribution (e.g., a mixture of relatively largeand relative small particles) or a narrow particle size distribution(e.g., substantially uniform particle size).

In one expression, the disclosed powdered titanium alloy composition maybe prepared as a physical mixture of at least two distinct powdercompositions. As one specific, non-limiting example, the disclosedpowdered titanium alloy composition may be prepared by mixing a firstpowder composition (a substantially pure titanium powder) with a secondpowder composition (a master alloy powder) in sufficient proportions toachieve the compositional limits recited in Table 1.

In another expression, the disclosed powdered titanium alloy compositionincludes a single powder component, and each powder particle of thesingle powder component has substantially the same composition.Specifically, each powder particle of the single powder component has acomposition within the compositional limits recited in Table 1. Such apowdered titanium alloy composition may be prepared, for example, byatomization, wherein a molten mass having a composition within thecompositional limits recited in Table 1 is forced through an orifice.

Also disclosed is a method for manufacturing articles using thedisclosed powdered titanium alloy composition. Referring to FIG. 1, oneembodiment of the disclosed method for manufacturing an article,generally designated 10, may begin at Block 12 with the step ofpreparing a powdered titanium alloy composition. The powdered titaniumalloy composition prepared at Block 12 may have a composition fallingwithin the compositional limits recited in Table 1.

At Block 14, the powdered titanium alloy composition may be compacted toform a shaped mass. Various compaction techniques may be used withoutdeparting from the scope of the present disclosure. As one example, thecompaction step (Block 14) may include die pressing. As another example,the compaction step (Block 14) may include cold isostatic pressing. Asanother example, the compaction step (Block 14) may include metalinjection molding. As yet another example, the compaction step (Block14) may include direct hot isostatic pressing.

At Block 16, the shaped mass may optionally be sintered. Sintering maybe required when the compaction step (Block 14) does not simultaneouslysinter/consolidate. For example, the sintering step (Block 16) mayinclude heating the shaped mass to an elevated temperature (e.g., about2,000° F. to about 2,500° F.) and maintaining the shaped mass at theelevated temperature for at least a minimum amount of time (e.g., atleast 60 minutes, such as about 90 minutes to about 150 minutes).

At Block 18, the shaped mass (e.g., the sintered shaped mass) mayoptionally be subjected to hot isostatic pressing (“HIP”) to reduce (ifnot eliminate) voids in the sintered shaped mass. For example, the hotisostatic pressing step (Block 18) may be performed at a pressureranging from about 13 ksi to about 16 ksi and a temperature ranging fromabout 1,475° F. to about 1,800° F., and the elevated pressure andtemperature may be applied for at least about 60 minutes, such as forabout 120 minutes to about 300 minutes.

At Block 20, the shaped mass (e.g., the HIPed and sintered shaped mass)may optionally be solution treated. For example, solution treatment mayinclude reheating the shaped mass from room temperature to a temperatureranging from about 1400° F. to about 1725° F., and maintaining attemperature for approximately 1 hour before rapidly cooling/quench usingvarious quench media, such as, but not limited to, water, ethyleneglycol, liquid polymer additives and gas atmospheres/partial pressuresthat could include argon, nitrogen and helium, individually or combined,along with forced atmosphere fan cooling.

At Block 22, the shaped mass (e.g., the solution treated, HIPed andsintered shaped mass) may optionally be aged. For example, aging mayinclude reheating the shaped mass from room temperature to a temperatureranging from about 900° F. to about 1400° F., and maintaining the shapedmass at temperature for about 2 to about 8 hours before cooling back toroom temperature.

Accordingly, the disclosed method 10 may be used to efficientlymanufacture articles of various shapes and sized, including articles(e.g., aircraft parts) having complex geometries. Because the articlesare produced to net (or near net) shapes, little or no machining isrequired to finalize the article, thereby significantly reducing bothmaterial and labor costs.

Articles formed from the disclosed powdered titanium alloy compositionmay exhibit excellent mechanical properties. Indeed, it is believed thatarticles formed from powdered forms of the titanium alloy compositionspresented in Tables 4 and 6 will exhibit an ultimate tensile strength(ASTM-E8) of at least 130 ksi, a yield strength (ASTM-E8) of at least120 ksi and an elongation (ASTM-E8) of at least 10 percent, which iscomparable to that achieved using wrought or powdered Ti-6Al-4V.Furthermore, it is believed that articles formed from powdered forms ofthe titanium alloy compositions presented in Tables 4 and 6 will exhibita fatigue limit of at least 95 ksi, which is comparable to that achievedusing wrought Ti-6Al-4V, but significantly better than that achievedusing powdered Ti-6Al-4V. Standard fatigue test methods can include, butare not limited to, alternating and mean stress imposed on variousfatigue test specimen designs, such as, but not limited to, rotationalbending, cantilever flat, axial dog bone, torsion, tension, three (3) orfour (4) point bending.

Examples of the disclosure may be described in the context of anaircraft manufacturing and service method 100, as shown in FIG. 2, andan aircraft 102, as shown in FIG. 3. During pre-production, the aircraftmanufacturing and service method 100 may include specification anddesign 104 of the aircraft 102 and material procurement 106. Duringproduction, component/subassembly manufacturing 108 and systemintegration 110 of the aircraft 102 takes place. Thereafter, theaircraft 102 may go through certification and delivery 112 in order tobe placed in service 114. While in service by a customer, the aircraft102 is scheduled for routine maintenance and service 116, which may alsoinclude modification, reconfiguration, refurbishment and the like.

Each of the processes of method 100 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof venders, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 3, the aircraft 102 produced by example method 100 mayinclude an airframe 118 with a plurality of systems 120 and an interior122. Examples of the plurality of systems 120 may include one or more ofa propulsion system 124, an electrical system 126, a hydraulic system128, and an environmental system 130. Any number of other systems may beincluded.

The disclosed titanium alloy composition may be employed during any oneor more of the stages of the aircraft manufacturing and service method100. As one example, components or subassemblies corresponding tocomponent/subassembly manufacturing 108, system integration 110, and ormaintenance and service 116 may be fabricated or manufactured using thedisclosed titanium alloy composition. As another example, the airframe118 may be constructed using the disclosed titanium alloy composition.Also, one or more apparatus examples, method examples, or a combinationthereof may be utilized during component/subassembly manufacturing 108and/or system integration 110, for example, by substantially expeditingassembly of or reducing the cost of an aircraft 102, such as theairframe 118 and/or the interior 122. Similarly, one or more of systemexamples, method examples, or a combination thereof may be utilizedwhile the aircraft 102 is in service, for example and withoutlimitation, to maintenance and service 116.

The disclosed titanium alloy composition is described in the context ofan aircraft; however, one of ordinary skill in the art will readilyrecognize that the disclosed titanium alloy composition may be utilizedfor a variety of applications. For example, the disclosed titanium alloycomposition may be implemented in various types of vehicle including,for example, helicopters, passenger ships, automobiles, marine products(boat, motors, etc.) and the like.

Although various embodiments of the disclosed titanium alloy compositionand article formed therefrom have been shown and described,modifications may occur to those skilled in the art upon reading thespecification. The present application includes such modifications andis limited only by the scope of the claims.

What is claimed is:
 1. A titanium alloy consisting essentially of: about7.0 to about 9.0 percent by weight vanadium; about 3.0 to about 4.5percent by weight aluminum; about 0.8 to about 1.5 percent by weightiron; about 0.14 to about 0.22 percent by weight oxygen; optionallyabout 0.8 to about 2.4 percent by weight chromium; and balance titanium.2. The titanium alloy of claim 1 wherein said vanadium is present atabout 7.0 to about 8.5 percent by weight.
 3. The titanium alloy of claim1 wherein said vanadium is present at about 7.5 to about 9.0 percent byweight.
 4. The titanium alloy of claim 1 wherein said aluminum ispresent at about 3.5 to about 4.5 percent by weight.
 5. The titaniumalloy of claim 1 wherein said aluminum is present at about 3.0 to about4.0 percent by weight.
 6. The titanium alloy of claim 1 wherein saidiron is present at about 0.9 to about 1.5 percent by weight.
 7. Thetitanium alloy of claim 1 wherein said iron is present at about 0.8 toabout 1.3 percent by weight.
 8. The titanium alloy of claim 1 whereinsaid oxygen is present at about 0.15 to about 0.22 percent by weight. 9.The titanium alloy of claim 1 wherein said oxygen is present at about0.14 to about 0.20 percent by weight.
 10. The titanium alloy of claim 1wherein said chromium is optionally present at about 1.8 to about 2.4percent by weight.
 11. The titanium alloy of claim 1 wherein: saidvanadium is present at about 7.0 to about 8.5 percent by weight; saidaluminum is present at about 3.5 to about 4.5 percent by weight; saidiron is present at about 0.9 to about 1.5 percent by weight; and saidoxygen is present at about 0.15 to about 0.22 percent by weight.
 12. Thetitanium alloy of claim 11 wherein said optional chromium is notpresent.
 13. The titanium alloy of claim 1 wherein: said vanadium ispresent at about 7.5 to about 9.0 percent by weight; said aluminum ispresent at about 3.0 to about 4.0 percent by weight; said iron ispresent at about 0.8 to about 1.3 percent by weight; said oxygen ispresent at about 0.14 to about 0.20 percent by weight; and said chromiumis present at about 0.8 to about 2.4 percent by weight.
 14. The titaniumalloy of claim 1 in powdered form.
 15. The titanium alloy of claim 14wherein said powdered form consists of a mixture of at least twodifferent powder compositions.
 16. The titanium alloy of claim 15wherein said mixture comprises a titanium powder and a master alloypowder.
 17. The titanium alloy of claim 14 wherein said powdered formconsists of a plurality of powder particles, and wherein each powderparticle of said plurality of powder particles has substantially thesame composition.
 18. The titanium alloy of claim 14 wherein saidpowdered form consists of a plurality of substantially spherical powderparticles.
 19. The titanium alloy of claim 18 wherein said plurality ofsubstantially spherical powder particles have a substantially uniformparticle size.
 20. An article formed from the titanium alloy of claim 1.21. An article formed from the titanium alloy of claim
 14. 22. A methodfor manufacturing an article comprising: compacting said powdered formtitanium alloy of claim 14 to form a shaped mass; and sintering saidshaped mass.
 23. The method of claim 22 wherein said compactingcomprises metal injection molding.
 24. The method of claim 22 furthercomprising subjecting said sintered shaped mass to hot isostaticpressing.
 25. The method of claim 22 further comprising solutiontreating and aging said sintered shaped mass.
 26. The titanium alloy ofclaim 1 in powdered form and consisting essentially of: about 7.0 toabout 8.5 percent by weight vanadium; about 3.5 to about 4.5 percent byweight aluminum; about 0.9 to about 1.5 percent by weight iron; about0.15 to about 0.22 percent by weight oxygen; and balance titanium. 27.The titanium alloy composition of claim 26 consisting of a plurality ofpowder particles, and wherein each powder particle of said plurality ofpowder particles has substantially the same composition.
 28. Thetitanium alloy composition of claim 26 consisting of a mixture of atleast two different powder compositions.
 29. The titanium alloycomposition of claim 28 wherein said mixture comprises a titanium powderand a master alloy powder.
 30. An article formed from the titanium alloycomposition of claim
 26. 31. The titanium alloy of claim 1 in powderedform and consisting essentially of: about 7.5 to about 9.0 percent byweight vanadium; about 3.0 to about 4.0 percent by weight aluminum;about 0.8 to about 2.4 percent by weight chromium; about 0.8 to about1.3 percent by weight iron; about 0.14 to about 0.20 percent by weightoxygen; and balance titanium.
 32. The titanium alloy composition ofclaim 31 wherein said chromium is present at about 1.8 to about 2.4percent by weight.
 33. The titanium alloy composition of claim 31consisting of a plurality of powder particles, and wherein each powderparticle of said plurality of powder particles has substantially thesame composition.
 34. The titanium alloy composition of claim 31consisting of a mixture of at least two different powder compositions.35. The titanium alloy composition of claim 34 wherein said mixturecomprises a titanium powder and a master alloy powder.
 36. An articleformed from the titanium alloy composition of claim 31.